<html>
<style>
#div1{
    background-color: aquamarine;
}

    #div2{
        margin: 0 auto;
        width: 400px;
        height: 400px;

    }
</style>
    <body>

       <div id="div1">
           <div id="div2">
               <h1>登录页面</h1>
               <form  action="user/user.php" method="post">
                   银行卡号:<input type="text" name="username" /><br />
                   密&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;码&nbsp;:<input type="password" name="password" /><br />
                                <input type="submit" value="提交">
               </form>
           </div>
       </div>

    </body>
</html>